This old train trestle and collapsed tunnel once allowed the railroad to negotiate the steep slopes of the Colorado Rockies.

Paleoamericans built these ancient walls high in the Colorado Rockies as part of an extensive hunting system.

These decaying bridges 1,000 feet high are a reminder of the skill it took to cross the Colorado Rockies by rail.

This razorback ridgeline has doubled as a scenic drive since the early 1900s.

The highest bridge in America was built for an almost unnervingly small amount of money.

When ecosystems collide in the arid Southwest.

One woman's UFO-themed campground, complete with self-built energy vortexes, UFO-themed weddings, and magic bushes.

Possibly the world's only drive-in movie theater with an attached motel.

This super steep hike ascends 2,000 feet in less than a mile.

The highest paved road in North America winds its way up Mount Blue Sky in Colorado to an altitude of 14,130 feet above sea level.

Baroque celebration of the end of the Great Plague of Vienna.

Trick water gardens from 1619 featuring a 200 piece mechanical theater powered by water.

Macabre astrological automaton clock dating to the late 1400s.

A monument to the three wars that led to German unification towers within a Berlin traffic circle.

This hauntingly beautiful cemetery outside a medieval citadel is full of winding paths and ivy-covered graves.

Nine centuries-old fortresses guard the walls of this medieval Romanian city.

This communist behemoth is the heaviest building in the world and a legacy of a brutal regime.

A fire once nearly devoured this gorgeous 14th-century Gothic cathedral.

The walls and streets of the ancient city are peppered with penises.

A monument to the man who almost killed Hitler.

Cold war icon and onetime "hole" in the iron curtain.

Soaring over 6,000 feet in the Bavarian Alps, this beer garden was once Hitler's 50th birthday present.

The big toe of this towering monument to a Croatian national hero is worn from years of superstitious rubbing.

A magnificent, long-abandoned castle built in the wake of the reconquest of Spain.